I don't know about letting off the gas, and I have an automatic so your experience might differ, but unless you plan on doing intake and exhaust mods, the tune isn't really worth it. All I did was add a cold air intake, no exhaust, and there's **** near no difference whatsoever. It might have eliminated the throttle lag but I really don't notice a difference, and it's just putting in premium gas for next to nothing. On the other hand, there's a iA FB group and the admin of the group installed the AEM cold air intake, a custom exhaust, a few other small things and with the tune, he was getting 120hp (an increase from 90hp stock) all dyno'ed and everything. He's actively trying to make the iA faster and working closely with someone on a turbo for the engine. So unless you plan on going all in, all you're doing is paying $500 for very little. Again, my experience is with an automatic, no idea about manual.

That sounds a bit disappointing. The OVT website claims an 8-16hp increase, and the tuner who handles Mazdas now (Raphael) told me that the engine would be more responsive, so I would hope that those (admittedly modest) improvements could be felt. I guess I'll think this over some more and maybe wait for some others to relay their thoughts.

Is the iA FB group "iA Society" or is there another one I should be joining? I'd love to hear how that one person got a 30% increase in horsepower! That would completely transform this car.

That sounds a bit disappointing. The OVT website claims an 8-16hp increase, and the tuner who handles Mazdas now (Raphael) told me that the engine would be more responsive, so I would hope that those (admittedly modest) improvements could be felt. I guess I'll think this over some more and maybe wait for some others to relay their thoughts.

Is the iA FB group "iA Society" or is there another one I should be joining? I'd love to hear how that one person got a 30% increase in horsepower! That would completely transform this car.

As for the tune, I don't know if it's just placebo, but after I got the tune, I swear the transmission downshifts faster when I press on the accelerator while cruising. 8-16hp isn't much tbh, even if it is a 10-15% increase in power compared to our engines, but the car already makes so little horsepower. Actual power is closer to 80 or 90 than the official rating of 106. You should probably try to get other owners' experience on the tune though, such as the members in the FB Group, before you make your decision. I don't feel a difference, but maybe the people there will let you know what to actually feel for, since I'm not exactly an expert.